Currently, fans are classified into two types, axial fans, and centrifugal blower. The axial fans have lower cost with a larger volume. The centrifugal blowers have thinner bladders with higher density and have higher cost and great noises.
There are two kinds of fans are used in power devices. One is brushless motor and the other is carbon brush motor. In the brushless motor, the coil is wound around the stator and the rotor is assembled with magnetic elements, which are contrary to the conventional carbon brush motor. Thereby for the burshless motor, the rectifier needs not to contact the carbon brush for conducting the rotor coil and rectification. Under the condition of no brush, the absorption and repulsion of the conduction stator coils and rotor magnetic elements will induce the operation of the motor. Therefore, currently, the brushless motors are used as power sources of axial fans and centrifugal blowers.
With reference to FIG. 1, the prior art fan structure is illustrated. The fan has a rotor 11 and a stator 12. The rotor 11 has a driving portion 111 and a magnetic element 112. The magnetic element 112 is assembled to the axial fan 111c, transmission shaft 111d, and the hub 111f. A bearing 111e is assembled to the transmission shaft 111d. 
The stator 12 includes an electrode sheet 121, a coil 122 and a seat 123. The electrode sheets 121 are assembled to the seat 123 and the coils 122 are wound around the stator flame 124 assembled on the seat 123.
Referring to FIG. 2, as illustrated in the drawing, the seat 123 is assembled to the frame 13. A circuit board 123a is assembled to the seat 123. In assembly, the magnetic element 112 is assembled in the hub 111f of the driving portion 111 and then the bearing 111e is assembled to a hollow chamber 123b in the seat 123. Then, the rotor 11 is pivotally installed to the stator 12 and the electrode sheets 121 are arranged corresponding to the magnetic element 112, but not contact with the magnetic element 112. Thereby after the coils 122 are conducted, stator 12 and rotor 11 will interact with one another.
However in above mentioned fan structure, since the arrangement of the magnetic element 112 and the electrode sheets 121, the thickness of the hub 111f cannot be reduced. However currently, the requirement of the fan is light, thin, short and small and has a larger capacity, while the prior art cannot achieve the object.